chore: enhance @comneed/textby package metadata and documentation

- Update package.json with comprehensive metadata
  - Add keywords for better NPM discoverability
  - Add author, repository, homepage, and bugs URLs
  - Add exports field for modern Node.js support
  - Add engines requirement (Node.js >=18.0.0)
  - Add prepublishOnly script for safer publishing
  - Bump version to 0.0.3

- Refactor README.md for accuracy
  - Remove unsupported features (mdx support claims)
  - Simplify template composition section (LiquidJS native feature)
  - Update API documentation to match actual implementation
  - Fix GitHub links to match monorepo structure
  - Add clear browser vs Node.js environment distinctions
  - Remove broken links to non-existent files

- Update CHANGELOG.md with v0.0.3 changes

Author: YuJM

packages/textby/CHANGELOG.md

@@ -1,5 +1,11 @@
 # @comneed/textby
 
+## 0.0.3
+
+### Patch Changes
+
+- 문서 개선
+
 ## 0.0.2
 
 ### Patch Changes